In certain surgical procedures, it is often highly desirable that smooth, precise, continuous incisions of a controlled depth be made. Irregular or discontinuous incisions may result in complications in healing and cause an irregular and perhaps enlarged scar. An imprecise incision may result in wound leakage or, in particular, in cataract surgery, in astigmatism.
With particular reference to cataract surgery, an initial incision is required at the sclera of the eye adjacent the cornea, the incised tissue being retracted to gain access to the lens of the eye. This incision is typically made along an arc following the curvature of the cornea. According to the prior art, the surgeon would by hand make an initial incision groove and following the groove, a subsequent intraocular incision to gain access to the lens.
The tissue of the sclera being incised typically has a thickness of between 300-700 microns. To limit the depth of cut, various scalpels have been devised as described in U.S. application Ser. No. 567,263 filed Dec. 30, 1983 now U.S. Pat. No. 4,552,146 and entitled "Disposable Ophthalmic Instrument for Performing Radial Keratotomy on the Cornea." The scalpel according to this application is adapted, using external gauges or the like, to have a selected depth of cut.
Cutting initially to the required depth, i.e., to incise the sclera, may result in an irregular or perhaps imprecise cut due to the resistance of the relatively large amount of tissue being incised and the fact that the incision is being made by hand. It would be advantageous, if an initial incision in the sclera of a nominal depth could first be made by the surgeon, the initial incision defining a line for the ultimate, complete incision to be made. To provide for a regular closure of the incision and to prevent wound leakage and astigmatism, the final incision is made at an angle (beveled). Using this initial, nominal depth incision, the surgeon could then retrace the incision cutting to the desired depth, the initial incision acting as a guide.
Given the problem and the desired solution, the applicant has achieved desired results by using a pair of scalpels. A first scalpel, having a preset nominal depth of cut, was used to make the initial incision. In that a relatively shallow depth cut was being made a smooth, precise and continuous initial incision could be made. Thereafter, a second scalpel having a deeper depth of cut was inserted into the initial incision and, using that initial incision as a guide, was positioned at the correct cutting angle and was moved to retrace the initial incision and complete the intraocular incision. The smooth, precise and continuous incision defined by this procedure has been found advantageous in that the incision when closed by suturing forms a watertight closure and prevents astigmatism.
Of course, it is to be understood that this procedure could apply equally well to surgeries other than those involved with the eye, such as cosmetic or other surgeries involving the skin where precise wound closure is necessary.
The use of two or more scalpels, one set to have a preset depth of cut, is costly since the scalpels are usually discarded. Further, the use of a pair of scalpels may be time consuming and frustrating to the surgeon since the surgeon must change from the first to the second scalpel.